Millau Viaduct

The 'Millau Viaduct' (French: le Viaduc de Millau) is a cable-stayed road-bridge that spans the valley of the River Tarn near Millau in southern France. Designed by French bridge engineer Michel Virlogeux in collaboration with British architect Norman Foster, it is the tallest vehicular bridge in the world, with one pier's summit at 343 metres (1,125 ft)—slightly taller than the Eiffel Tower and only 38 m (125 ft) shorter than the Empire State Building. It was formally dedicated on 14 December 2004 and opened to traffic two days later.

Location
Millau Viaduct's coordinates are 44.077165° N 3.022887° E. Before the bridge was constructed, traffic had to descend into the Tarn River valley and pass along the route nationale N9 near the town of Millau, causing heavy congestion at the beginning and end of the July and August vacation season. The bridge now traverses the Tarn valley above its lowest point, linking the causse du Larzac to the causse rouge, and is inside the perimeter of the Grands Causses regional natural park.
The bridge forms the last link of the A75 autoroute, (la Méridienne) from Clermont-Ferrand to Pézenas (to be extended to Béziers by 2010). The A75, with the A10 and A71, provides a continuous high-speed route south from Paris through Clermont-Ferrand to the Languedoc region and through to Spain, considerably increasing the speed and reducing the cost of vehicle traffic travelling along this route. Many tourists heading to southern France and Spain follow this route because it is direct and without tolls for the 340 km between Clermont-Ferrand to Pézenas, except for the bridge itself.
The Eiffage group operates the viaduct as a toll bridge, with the toll currently (Nov 2006) set at €5.10 for light automobiles (€6.80 during the peak months of July and August). The bridge was constructed by the Eiffage group, which also built the Eiffel Tower, under a government contract which allows the company to collect tolls for up to 75 years

Description
The Millau Viaduct consists of an eight-span steel roadway supported by seven concrete piers. The roadway weighs 36,000 tons and is 2,460 m long, measuring 32 m wide by 4.2 m deep. The six central spans each measure 342 m with the two outer spans measuring 204 m. The roadway has a slope of 3% descending from south to north, and curves in plan section on a 20 km radius to give drivers better visibility. It carries two lanes of traffic in each direction.
The piers range in height from 77–246 m, and taper in their longitudinal section from 24.5 m at the base to 11 m at the deck. Each pier is composed of 16 framework sections, each weighing 2,230 tons. These sections were assembled on site from pieces of 60 tons, 4 m wide and 17 m long, made in factories in Lauterbourg and Fos-sur-Mer by Eiffage. The piers each support 97 m tall pylons. The piers were assembled first, together with some temporary supports, before the decks were slid out across the piers by satellite-guided hydraulic rams that moved the deck 600 mm every 4 minutes.
The viaduct is the tallest vehicular bridge in the world, nearly twice as tall as the previous tallest vehicular bridge in Europe, the Europabrücke in Austria.
The Millau Viaduct is the second highest vehicular bridge measured from the roadway elevation. Its deck, at approximately 270 m above the Tarn, is slightly higher than the New River Gorge Bridge in West Virginia in the United States, which is 267 m above the New River. The Royal Gorge Bridge in Colorado, United States has a deck considerably higher than either, at 321 m above the Arkansas River.

Construction
Construction began on 10 October 2001 and was intended to take three years, but weather conditions put work on the bridge behind schedule. A revised schedule aimed for the bridge to be opened in January 2005. The viaduct was officially inaugurated by President Chirac on 1 December 2004 to open for traffic on 16 December, several weeks ahead of the revised schedule. The construction of the bridge is depicted in a documentary of the Discovery Channel 'Megastructures' series.

Implementation
The bridge deck was constructed on land at the ends of the viaduct and rolled lengthwise from one tower to the next, with seven temporary added towers also in place. The movement was accomplished by a computer-controlled system of pairs of wedges under the deck; the upper and lower wedges of each pair pointed in opposite directions. These were hydraulically operated, and moved repeatedly in the following sequence:
Lower wedge slides under the upper wedge, raising it to the roadway above and then forcing the upper wedge still higher to lift the roadway.
Both wedges move together, advancing the roadway a short distance.
Lower wedge retracts from under the upper wedge, lowering the roadway and then allowing the upper wedge to drop away from the roadway.
Upper wedge moves backward, placing it into position farther (back) along the roadway, ready to repeat the cycle and advance the roadway again.

Costs and resources
The bridge's construction cost up to €394 million, with a toll plaza 6 km north of the viaduct costing an additional €20 million. The builders, Eiffage, financed the construction in return for a concession to collect the tolls for 75 years, until 2080. However, if the concession is very profitable, the French government can assume control of the bridge in 2044.
The project required about 127,000 m³ of concrete, 19,000 metric tons of steel for the reinforced concrete, and 5,000 metric tons of pre-stressed steel for the cables and shrouds. The builder claims that the bridge's lifetime will be at least 120 years.

Statistics
2,460 m: total length of the roadway
7: number of piers
77 m: height of Pier 7, the shortest
343 m: height of Pier 2, the tallest (245 m at the roadway's level)
87 m: height of a pylon
154: number of shrouds
270 m: average height of the roadway
4.20 m: thickness of the roadway
32.05 m: width of the roadway
85,000 m³: total volume of concrete used
290,000 tonnes: total weight of the bridge
10,000–25,000 vehicles: estimated daily traffic
€4.90–6.50: typical automobile toll, as of 2005
20 km: horizontal radius of curvature of the road deck